CH 1000 MOD 1 REVIEW HW

CH1000 Fundament als of Chemistry Module 1 – Chapter 2

Scientific Notation

Scientific notation is used to represent very large or small numbers in math and science.

Writing a number as the product of a number between 1 and 10 multiplied by 10 raised to some power is called scientific notation

For help on using scientific notation on a calculator, visit: https://www.youtube.com/watch? v=qE2BvtGiEMs

Measurement and Uncertainty

•A measurement is always expressed by a numerical value together with a unit of measurement

•The certainty of a measurement is dependent upon the calibration of the instrument

•It is customary when recording a measurement to include all of the digits that are known plus one digit that is estimated.

•The estimated digit introduces a level of uncertainty into the measurement. It is because of this uncertainty that every number that expresses a measurement can only have a limited number of digits

•These digits, used to express a measured quantity are known as significant figures.

Significant Figures

3 Rules

Nonzero digits • All nonzero digits are significant

Exact Numbers • Exact numbers occur in simple counting operations • Direct conversions (12 inches in 1 foot) are also

considered exact numbers • Exact numbers have no uncertainty

Zeros • Only significant when:

• Between nonzero digits • At the end of a number that includes a decimal point

• Not significant when: • Before the first nonzero digit • At the end of a number without a decimal point

Significan t Figures in Calculatio ns

For addition and subtraction use the following rules: Count the number of significant figures in the decimal portion ONLY of each number in the problem Add or subtract in the normal fashion Your final answer may have no more significant figures to the right of the decimal than the LEAST number of significant figures in any number in the problem

For multiplication and division use the following rule: The LEAST number of significant figures in any number of the problem determines the number of significant figures in the answer. (You are now looking at the entire number, not just the decimal portion) This means you have to be able to recognize significant figures in order to use this rule Example: 5.26 has 3 significant figures 6.1 has 2 significant figures So, 5.26*6.1 = 32

To check your answers: https://www.sigfigscalculator.com/

The Metric System Also known as the International or SI system, it is a decimal system of units for measurements of mass, length, time and other physical quantities

Common prefixes and Numerical values for SI units

SI Standard Units of Measurement

Unit Conversion s

LENGTH (MM TO M):

MASS (MG TO G):

VOLUME (L TO ML):

Temperatu re

DEGREES CELSIUS = °C KELVIN (ABSOLUTE) = K

DEGREES FAHRENHEIT = °F

K=°C + 273.15 °F = (1.8 * °C) +32 °C = (°F – 32)/1.8

HEAT IS THE FLOW OF ENERGY DUE TO TEMPERATURE DIFFERENCE. HEAT ALWAYS MOVES FROM HIGHER TEMPERATURE TO

LOWER TEMPERATURE

Density

• Ratio of mass to volume

Density

• Ratio of density of a substance to the density of water at 4°C

Specific Gravity

Reading Review • How many significant figures are in 0.00025? • Express 0.00025 in scientific notation. • Draw a solution map from yd to m. • What are the three most common temperature

scales?

• What is the difference between density and specific gravity?